1. Field of the Invention
The present invention relates to a linear slide fastener in which thermoplastic resin monofilament is formed into a coil-like or zigzag-like linear fastener element having a particular shape and this linear fastener element is attached to a side edge of a fastener tape with a fixing thread such as various types of sewing threads.
2. Description of the Related Art
In a coil-like fastener element 102 of a conventional linear slide fastener disclosed by U.S. Pat. No. 3,149,388, when the coil-like fastener element 102 is sewed by a sewing-machine on a side edge of a fastener tape 104 with a sewing thread 106, a concave portion 114 is formed in a central portion of an upper leg portion 112 of the coil-like fastener element 102 in order to protect the sewing thread 106 from being damaged by sliding a slider and the sewing thread 106 is accommodated in this concave portion 114 for protection as shown in FIG. 12. In this coil-like fastener element 102, a coupling head 110 and an inverted portion 111 of the fastener element 102 are formed in an equal height so as to protect the sewing thread 106.
In the coil-like fastener element 102 shown in FIG. 12, since the coil-like fastener element 102 has the concave portion 114 for accommodating the sewing thread 106 and sizes of portions of the coil-like fastener element 102 on the right and left sides of the concave portion 114, i.e., on a side of the coupling head 110 and on a side of the inverted portion 111, are substantially same, the coil-like fastener element 102 has to be formed larger than actually needed. There is no need to form an inverted portion 111 of the coil-like fastener element 102 so large. Because forming the inverted portion 111 in an equal size to the coupling head 110 leads to forming the coil-like fastener element 102 larger than actually needed, this results in waste of resource and an increase in cost.